This invention relates to hair coloring preparations containing substantive hair dyes. Hair coloring preparations of the type in question contain substantive hair dyes in a cosmetic carrier. In addition, they often contain oxidation dye precursors for obtaining certain shades. The cosmetic carriers used for the substantive hair dyes and, optionally, oxidation dye precursors include creams, emulsions, gels, shampoos, foam aerosols and other preparations which are suitable for application to the hair.
In addition to oxidation dyes, which are formed by oxidative coupling of one or more developer components with one another or with one or more coupler components, substantive hair dyes play a particularly important part in the dyeing of hair. The advantage of substantive dyes is that they may be used without the addition of oxidizing agents. The substantive dyes used are primarily compounds belonging to the group of nitrobenzene derivatives. They are used either on their own or in combination with other substantive dyes, such as anthraquinone dyes, indophenols, or with oxidation dyes.
Good hair coloring preparations have to form the required shades with sufficient intensity. They must also be readily absorbed by human hair without excessively staining the scalp. The hair colorings obtained have to be stable to light, heat, perspiration, shampoos and also to the chemicals used in the permanent waving of hair. Finally, they must be safe to use both from the toxicological and from the dermatological viewpoint.
Among substantive nitrobenzene derivatives, nitroanilines and their derivatives occupy a special position because some of these dyes form intensive, light-stable shades. Unfortunately, known substantive nitroaniline dyes are not fast to washing, i.e. they bleed after repeated washing of the hair. In addition, substantive dyes have to be compatible with other dyes, for example with oxidation dye precursors and with the components normally present in oxidation hair dyes, because substantive dyes and oxidation dyes are often used in combination for changing shades. Accordingly, high stability to reducing agents and oxidizing agents is essential.